The present invention relates to metallurgy, and more particularly to continuous casting apparatus.
The invention is especially well suited for application with continuous-casting machines used for casting ferrous metals and alloys thereof, said machines featuring either horizontal or inclined arrangement of the mold connected to the tundish by a refractory conduit.
Prior to starting the casting operation on a continuous-casting machine, a dummy bar assembly, equipped with a head section fixedly attached to a carrying section, is fed into the mold. To prevent leakage of the molten metal through the gap formed between the mold walls and the dummy-bar head, the gap is packed with a heat-resistant material, such as asbestos string.
The gap is sealed with refractory material at the side of the dummy-bar head facing the metal being poured into the mold cavity. The dummy bar is then connected with the mold and the tundish to be filled with the molten metal.
As casting commences, the dummy bar is withdrawn from the mold together with the cast product. On completion of the casting process, the refractory conduit, connecting the mold to the tundish, is disposed of. Preparation of such a machine for the continuous casting operation, the casting operation itself and the disposal of the conduit make up a complete casting or operating cycle.
Recently, there have been developed refractory materials for the fabrication of conduits capable of withstanding several casting cycles. The disposal of conduits which are still serviceable and usable in subsequent casting cycles is necessitated by the difficulties encountered during the sealing operation to be performed with the dummy bar being fed into the mold. The packing of the gap, formed between the head section and the mold wall, can only be accomplished if approached from the side of the dummy-bar head facing the metal being cast within the mold. Therefore, the destruction of the still serviceable conduit results in higher production costs and lower operating rates.
U.S. Pat. No. 3,262,161 describes a dummy bar for use on a continuous casting machine equipped with a head section having its surface, looking in the direction of the metal being cast, fitted with an elastic heat-resistant annular packing. As the dummy bar is fed into the mold, the edges of the packing fit in the gap between the mold walls and the lateral surfaces of the dummy-bar head.
However, the use of the dummy bar disclosed in the patent referred to above is associated with certain difficulties. There is a danger that reliable sealing will not be ensured with the dummy bar run up into a mold cavity which has its outlet opening of a smaller cross section than that of its inlet opening. The heat-resistant elastic material used for sealing must have, practically, no residual strain and be capable of increasing its thickness from 1-2 mm up to 3-10 mm.
The sealing material which exhibits elasticity and resistance to heat at high temperatures is most likely to be very expensive. The use of elastic and heat-resistant materials for sealing a dummy-bar head not tapered relative to the mold walls may also turn out to be economically unjustifiable.
F.R.G. Pat. No. 1,954,107 discloses a dummy bar wherein the gap between the dummy-bar head and the mold walls is packed with a heat resistant material, such as asbestos, from the side of feeding of the molten metal.
However, with a conventional mold having its face wall looking in the direction of delivery of the molten metal, it will be impossible to fill in the gap between the dummy-bar head and the lateral surfaces of the mold wall from the face side thereof.
Therefore, it becomes necessary to fill in the gap from the side of exit of the cast ingot.
However, if packing of the gap is attempted from the side from which the cast ingot issues, reliable packing will not be ensured throughout the entire perimeter of the dummy-bar head and the dummy bar may even be jammed inside the mold.